ACS Photon. 2, 165–171 (2015)

The development of efficient and truly subdiffraction-sized laser sources for nanophotonics is still a core goal of plasmonics research. Now, researchers in Japan at the University of Tokyo have demonstrated lasing in GaAs−AlGaAs core−shell nanowires with 150 nm diameters positioned in contact with a silver film. Near-infrared lasing, with emission in the ∼800–850 nm wavelength range, was achieved under optical pumping at temperatures up to 125 K. The team emphasizes that some previous plasmonic nanowire lasing demonstrations employed thin films of low-index dielectric material between the metal and the high-index semiconductor wire to mitigate loss and quenching effects by using 'hybrid' plasmon waveguide modes. Instead, the researchers used nanowires directly in contact with the metal film and argue that the result is a better overlap between the optical mode and the gain media (semiconductor wire). The fundamental mode experiences very high losses, so the team concentrated on achieving lasing of higher-order modes that are less lossy but exhibit more field penetration into surrounding (less lossy) media. A low lasing threshold of 1.0 kW cm−2 was achieved at a temperature of 8 K. The team attributed this low value not only to the use of higher-order modes but also to a smooth silicon substrate and a single-crystalline silver film.